Flexible display device

ABSTRACT

A flexible display device ( 10 ) is disclosed. The flexible display device comprises a flexible substrate ( 12 ), a number of display pixels ( 14 ) arranged in a form of rows and columns on the surface of the substrate, a number of grooves ( 16 ) in the surface of the substrate each of which is formed in between adjacent two rows or columns of the display pixels ( 14 ), and connection lines ( 18 ) for electrically interconnecting the plurality of display pixels ( 14 ), thereby providing flexibility to the display device and, at the same time, minimizing the propagation of mechanical stress caused when the display device is bent or rolled. A method of manufacturing the display device is also disclosed.

FIELD OF THE INVENTION

[0001] The present invention relates generally to a display device. Moreparticularly, the invention relates to a flexible display device, whichcan be rolled up in a preferential direction. The invention also relatesto a method of manufacturing such flexible display devices.

BACKGROUND OF THE INVENTION

[0002] In general, a display panel device consists of a substrate layer,a number of display pixels disposed on the surface of the substrate, andpixel switching circuitry. The display pixels are arranged in a form ofplural rows and columns.

[0003] Conventionally, flexible substrates such as a plastic substratehave been utilized to provide a mechanical flexibility to displaydevices. However, there has been a limitation to the degree offlexibility since the flexibility of the display panel relies on onlythat of the plastic substrate. In addition, the mechanical stress causedby bending or flexing is propagated throughout the whole displayingarea, particularly the display pixels. Therefore, the displayperformance characteristics of the pixels are adversely affected so thatit can not work properly as a display device, especially whenexcessively bent or severely flexed.

[0004] Accordingly, there is a need to solve the conventional problemsnoted above and to provide a novel flexible display device in which itsflexibility can be maximized and the propagation of mechanical stresscan be minimized, without damaging the display performance.

SUMMARY OF THE INVENTION

[0005] According to one aspect of the present invention, there isprovided a flexible display device. The display device comprises (a) aflexible substrate; (b) a plurality of display pixels arranged in a formof rows and columns on the surface of the substrate; (c) a plurality offirst grooves in the surface of the substrate, the first groove beingformed in between adjacent two rows or columns of the display pixels,thereby providing flexibility to the display device and, at the sametime, minimizing the propagation of mechanical stress caused when thedisplay device is bent or rolled; and (d) a plurality of connectionlines for electrically interconnecting the plurality of display pixels.The display device can further include a plurality of second grooves,each of which is formed in between adjacent two columns or rows of thedisplay pixels thereby enhancing the flexibility of the display device,the first and second grooves being substantially perpendicular to eachother.

[0006] According to another aspect of the present invention, there isprovided a flexible display device. The display device comprises (a) aflexible substrate having a first and second surfaces; (b) a pluralityof display pixels arranged in a form of rows and columns on the firstsurface of the substrate; (c) a plurality of first parallel grooves inthe first surface of the substrate, the first groove being formed inbetween adjacent two rows or columns of the display pixels, therebyproviding flexibility to the display device and, at the same time,minimizing the propagation of mechanical stress caused when the displaydevice is bent or rolled; and (d) a plurality of connection lines forelectrically interconnecting the plurality of display pixels. Theconnection lines comprise: (a) a plurality of row connection linesprovided on the second surface of the substrate, each row connectionline corresponding to each respective row of display pixels; (b) aplurality of column connection lines provided on the second surface ofthe substrate, each column connection line corresponding to eachrespective column of display pixels; and (c) a plurality of verticalconnection lines each connecting each display pixel on the first surfacewith a corresponding row or column connection line on the secondsurface, wherein an insulation layer is provided between the row andcolumn connection lines.

[0007] According to one aspect of the present invention, there isprovided a method of manufacturing a flexible display device. The methodcomprises the steps of: (a) providing a flexible substrate having afirst and second surface; (b) forming a plurality of first parallelgrooves in the first surface of the substrate, each adjacent twoparallel grooves defining a pixel area therebetween; (c) providing aplurality of display pixels on the pixel area such that the displaypixels are arranged in a pattern of rows and columns; and (d) providinga plurality of connection lines to electrically interconnect the displaypixels. The method can further include a step of forming a plurality ofsecond parallel grooves in the first surface of the substrate such thatthe second groove is substantially perpendicular to the first groove.The step of providing a plurality of connection line comprises steps of:(a) providing a first connection line to connect the first surface withthe second surface of the substrate; and (b) providing a secondconnection line on the second surface of the substrate such that thefirst connection line serves to electrically connect the display pixelon the first surface to the second connection line on the secondsurface. The step of providing a first connection line comprises stepsof: (a) forming a through-hole passing through the first and secondsurfaces of the substrate; and (b) carrying out metallization in thethrough-hole.

[0008] A further understanding of other aspects, features, andadvantages of the present invention will be realized by reference to thefollowing description, appended drawings and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The embodiments of the invention will be described with referenceto the accompanying drawings, in which:

[0010]FIG. 1 illustrates a schematic sectional view of a flexibledisplay device according to the first embodiment of the presentinvention;

[0011]FIG. 2 shows the top view of the flexible display device of FIG.1;

[0012]FIG. 3 is a schematic representation of a sectional view of aflexible display device according to the second embodiment of thepresent invention;

[0013]FIG. 4 depicts the top view of the flexible display device of FIG.3;

[0014]FIG. 5 is a schematic cross-sectional view taken along the lineA-A in FIG. 4 with the pixel electronics omitted;

[0015]FIG. 6 is a schematic cross-sectional view taken along the lineB-B in FIG. 4 with the pixel electronic omitted;

[0016]FIG. 7 illustrates a top plan view of a flexible display deviceaccording to the third embodiment of the invention;

[0017]FIGS. 8a to 8 j sequentially illustrate a manufacturing process ofthe flexible display device in accordance with the fourth embodiment ofthe invention; and

[0018]FIGS. 9a to 9 r show sequential steps of a manufacturing processof the flexible display device in accordance with the fifth embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0019] In FIGS. 1 and 2, there is schematically illustrated a flexibledisplay device in accordance with the first embodiment of the presentinvention, which is generally denoted by a reference numeral 10. FIG. 1is the cross-sectional view of the display device, and FIG. 2illustrates the top plan view thereof.

[0020] Referring to FIGS. 1 and 2, the flexible display device 10comprises a flexible substrate 12 such as a plastic substrate, aplurality of display pixels 14 provided on the surface of the substrate12, a plurality of grooves 16 formed between the display pixels 14, anda plurality of connection lines 18 for electrically interconnecting thedisplay pixels 14. In this embodiment, the display pixels 14 arearranged in a pattern of plural rows and columns as is shown in FIG. 2.The groove 16 can be formed in between any adjacent rows or columns ofthe display pixels, for example, in a regular pattern. In thisembodiment, the grooves 16 are provided in between every adjacent twocolumns of display pixels and formed substantially parallel to thecolumns. The connection lines 18 include a plural of column connectionlines 18C and a plural of row connection lines 18R, which serve toelectronically interconnect the columns and rows of display pixelsrespectively, as is illustrated in FIGS. 2. An insulation layer (notshown in FIGS. 1 and 2) is provided between the row and columnconnection lines 18R and 18C, which are substantially perpendicular toeach other.

[0021] The grooves 16 define a pixel area 13 in-between where thedisplay pixels 14 are placed. Accordingly, by virtue of the grooves 16,the pixel area 13 is mechanically isolated, and the whole display device10 is provided with a greater flexibility, especially to the extent thatit can be rolled up or folded. The mechanical isolation of the pixelarea 13 serves to minimize the stress propagation from the substrate 12to the pixel area 13, i.e., the display pixels 14 when rolled or bent.That is, the minimal influence on display performance characteristicscan be achieved. Therefore, the display device 10 of the invention canbe stored in a compact rolled state, for example, in a cylindricalcasing, and can be flattened out when in use. Furthermore, the flexibledisplay device 10 can operate even when it remains bent or wrappedaround a cylindrical surface.

[0022] In the embodiment of FIGS. 1 and 2, although the display device10 is provided with a plural of columnar grooves 16 only, it can furtherinclude a plural of row grooves 16R as illustrated in FIG. 7. Each rowgroove 16R is provided in between each adjacent two rows of displaypixels, thereby improving the flexibility of the display device. Thecolumn and row grooves 16C, 16R are substantially perpendicular to eachother.

[0023] As illustrated in FIG. 1, the grooves 16 can take either arectangular or rounded cross-section.

[0024] Each display pixel 14 includes an electro-luminescent displaylayer such as a polymer or organic emitting diode (OLED) and pixelelectronics such as thin-film-transistor based switching circuitry. Thepixel electronics can be integrated in a stacked pixel configuration onthe pixel area 13.

[0025] FIGS. 3 to 6 schematically depict a flexible display device 10 inaccordance with the second embodiment of the present invention. FIG. 3is the cross-sectional view of the display device, and FIG. 4illustrates the top plan view thereof. FIGS. 5 and 6 are cross-sectionalviews taken along the lines A-A and B-B respectively in FIG. 4.

[0026] Similar to the previous embodiment of FIGS. 1 and 2, the flexibledisplay device 10 of FIGS. 3 to 6 comprises a flexible substrate 12 suchas a plastic substrate, a plurality of display pixels 14 provided on thesurface of the substrate 12, a plurality of grooves 16 formed betweenthe display pixels 14, and a plurality of connection lines 17 and 18 forelectrically interconnecting the display pixels 14. Likewise, theconfiguration of the elements is essentially identical in bothembodiments, except for that of the connection lines.

[0027] Referring to FIGS. 3 to 6, the structure of the connection lineof this embodiment will be described hereafter in greater detail.

[0028] In this embodiment, the connection line for electricallyinterconnecting the display pixels comprise a plural of row connectionlines 18R, a plural of column connection lines 18C, and a plural ofvertical connection lines 17. According to this embodiment, the row andcolumn connection lines 18R and 18C are provided on the opposite side tothe surface of the substrate 12 where the display pixels 14 aredisposed. An insulation layer 19 a is provided between the row andcolumn connection lines 18R, 18C, as clearly illustrated in FIGS. 5 and6. The vertical connection line 17 serves to connect each display pixel14, for example a pixel contact 15 (on which the display pixel isintegrated) with each corresponding row or column connection lines. Morespecifically, the vertical connection line 17 includes a column verticalconnection line 17C and a row vertical connection line 17R. In thisembodiment, each display pixel 14 is provided with a row verticalconnection line 17R and a column vertical connection line 17C, whichelectronically connect the display pixel 14 to a corresponding row andcolumn connection lines 18R, 18C respectively, as clearly depicted inFIGS. 5 and 6. Further detail of the connection lines 17, 18 will bedescribed hereinafter, in conjunction with manufacturing processes ofthe flexible display of the invention.

[0029] In FIG. 7, there is schematically shown a top plan view of aflexible display device in accordance with the third embodiment of theinvention. As noted above and illustrated in FIG. 7, the display deviceof the invention can be further provided with a plurality of row grooves16R together with a plurality of column grooves 18C, thereby improvingthe flexibility of the display device. Likewise, each row groove isformed in between each adjacent two rows of display pixels 14.

[0030] According to another embodiment of the invention, there isprovided a method of manufacturing the flexible display devicesdescribed above. The method, in general, includes a step of forming anumber of parallel grooves in the surface of a flexible substrate, suchthat a columnar pixel area is defined between each adjacent two groovesas illustrated in FIGS. 2 and 4. The parallel grooves can consist of aplurality of parallel row grooves and a plurality of parallel columngrooves. In this case, each adjacent two row grooves define an isolatedpixel area in combination with each adjacent two column grooves, asshown in FIG. 7. According to the method, then, a number of displaypixels are provided on the pixel area defined between the grooves suchthat the display pixels are arranged in a form of parallel rows andcolumns, and the row and column of pixels are parallel with the row andcolumn grooves respectively. The method of the invention also includes astep of forming a connection line to electronically interconnect thedisplay pixels, depending on the design of the display device. Detailsof the above steps will be described hereinafter, in conjunction withFIGS. 8a to 9 r.

[0031] It is noted that the order of the steps of the method, which isdescribed above and will be further described hereafter, can be switchedwith each other, depending on the design of the display, or undercertain manufacturing conditions and circumstances.

[0032] In FIGS. 8a to 8 j, there is sequentially and schematicallyillustrated a method of manufacturing a flexible display device inaccordance with the fourth embodiment of the invention. The method willbe explained in greater detail hereafter.

[0033]FIGS. 8a to 8 d show, in sequence, a process of forming aplurality of grooves in the surface of a flexible substrate 12. Forconvenience of the illustration and description, there is shown only twoparallel grooves 16, between which a pixel area 13 is defined. Thegrooves 16 can be formed in the flexible plastic substrate 12 by using,for example, a metal (or other) masking technique and reactive ionetching (RIE) process in an atmosphere of CF₄+O₂ mixture. That is, athin-film metal 12 a is first deposited on the flexible substrate 12 andthen patterned according to a desired outline and dimensions of thegrooves as shown in FIG. 8b. Then, the metal-patterned substrate istransferred into a RIE chamber, where the area of the substrate surfacewhich is free from the metal 12 a is etched and eventually results inthe grooves 16 as depicted in FIG. 8c. After RIE-etching of thesubstrate, the metal mask 12 a is removed by using a wet etchant, or thelike as shown in FIG. 8d. Alternatively, the grooves in the plasticsubstrate can be formed by means of a laser micromachining process or aprojection laser micromachining process, which are well-known in theart.

[0034] Depending on the requirements of pixel size and the desireddegree of bending (radius of curvature), the depth and width of thegrooves can be controlled during the above processes such that themechanical integrity of the substrate can be maintained while minimizingthe influence on display performance characteristics.

[0035]FIGS. 8e to 8 j sequentially illustrate the step of providing adisplay pixel 14 and a connection line 18 between adjacent pixels. Aswell-known in the art, the display pixel 14 associates various pixelelectronics, including conducting layers, several dielectric layers 11a, 11 c and 11 d, and can electrode 11 b, a source and drain metal 11 f,an OLED (Organic Light Emitting Diode) cathode 11 e, an organic layer 11g, or the like. Although an OLED device is illustrated as a displaypixel, various other types of pixel devices can be integrated togetherwith other necessary components. The above display pixel and relatedcomponents, and the connection line 18 can be formed by means of variousconventional semiconductor processes such as lithography or the like.

[0036] In FIGS. 9a to 9 r, there is sequentially and schematicallyillustrated a method of manufacturing a flexible display device inaccordance with the fifth embodiment of the invention. The method willbe explained in greater detail, referring to the flexible display deviceshown in FIGS. 3 to 6.

[0037] In this embodiment, the step of forming a connection line betweenthe display pixels is different from that of the previous one. Othersteps are essentially identical with those of the previous embodiment.That is, the step of forming the connection lines includes steps ofproviding a first connection line perforating a flexible substrate, andproviding a second connection line on the opposite side to the surfaceof the substrate where the display pixels are placed, such that thefirst connection line serves to electrically connects the display pixelon the surface to the second connection line. In the figures, the firstconnection line is denoted by reference numerals 17C or 17R, and thesecond connection line by 18C or 18R. The first connection lines 17C,17R correspond to the vertical connection lines 17C, 17R in FIGS. 3 to6.

[0038] According to this embodiment of the invention, the step ofproviding a first connection line comprises steps of forming athrough-hole passing through the substrate, and carrying outmetallization in the through-hole.

[0039]FIGS. 9a to 9 f show the forming procedures of a first connectionline 17 C or 17R. As illustrated in FIGS. 9a to 9 d, the step of makinga through-hole 11 is similar to the groove forming process describedabove in conjunction with FIGS. 8a to 8 d. That is, a metal masking andpatterning process and a reactive ion etching (RIE) process, a lasermicromachining process, or a projection laser micromachining process canbe utilized, which are well-known processes in the art. A metal layer 12b such as an Al layer is provided on the opposite side to the substratesurface where the metal masking 12 a is deposited. The metal layer 12 bis used for providing the second connection lines 18C and 18R insubsequent steps of the method.

[0040]FIGS. 9e and 9 f schematically illustrate the step of metallizingthe through-holes 11 to forming the first connection lines 17C and 17R.Various conventional processes can be used for metallization of thethrough-holes 11, including an electro- or electroless depositionprocess.

[0041] In FIGS. 9g to 9 l, there is schematically depicted the step ofproviding the second connection lines 18C and 18R. Specifically, asshown in FIG. 9h, by patterning the metal layer 12 b, a secondconnection line 18C is formed, which corresponds to the columnconnection line in FIGS. 4 to 6. Then, a first insulation layer 19 asuch as a dielectric layer is deposited over the second connection line18C. As illustrated in FIGS. 9j to 9 l, opening vias in the insulationlayer 19 a, and deposition and patterning another metal layer arecarried out to provide another second connection line 18R, whichcorresponds to the row connection line in FIGS. 4 to 6. Then anotherinsulation layer 19 b such as a dielectric encapsulation layer isprovided above the second connection line 18R, as shown in FIG. 9l.

[0042] Subsequently, as shown in FIG. 9m, the grooves 16 are formed bymeans of the same processes noted above, in conjunction with theprevious embodiment of FIGS. 8a to 8 j. The grooves 16 define a pixelarea 13.

[0043] Similar to FIGS. 8e to 8 j, FIGS. 9n to 9 r schematically andsequentially illustrate the step of providing a display pixel 14. Aswell-known in the art, the display pixel 14 associates various pixelelectronics, including conducting layers, several dielectric layers, aelectrode, a source and drain metal, an OLED cathode, an organic layer,or the like. Although an OLED device is illustrated as a display pixel,various other types of pixel devices can be applied to the presentinvention. The above display pixel and related components can be formedby means of various conventional semiconductor processes such aslithography or the like.

[0044] While this invention has been described with reference to severalspecific embodiments, the description is illustrative of the inventionand is not to be construed as limiting the invention. Variousmodifications and variations may occur to those skilled in the artwithout departing from the true spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A flexible display device comprising: (a) aflexible substrate; (b) a plurality of display pixels arranged in a formof rows and columns on the surface of the substrate; (c) a plurality offirst grooves in the surface of the substrate, each first groove beingformed in between adjacent two rows or columns of the display pixels,thereby providing flexibility to the display device and, at the sametime, minimizing the propagation of mechanical stress caused when thedisplay device is bent or rolled; and (d) a plurality of connectionlines for electrically interconnecting the plurality of display pixels.2. A flexible display device according to claim 1, further comprising aplurality of second grooves, each of which is formed in between adjacenttwo columns or rows of the display pixels thereby enhancing theflexibility of the display device, the first and second grooves beingsubstantially perpendicular to each other.
 3. A flexible display deviceaccording to claim 1, wherein the first groove is provided in betweeneach adjacent rows or columns of display pixels.
 4. A flexible displaydevice according to claim 1, wherein the connection line comprises acolumn connection line and a row connection line, and an insulationlayer is provided between the column and row connection lines.
 5. Aflexible display device according to claim 1, wherein the groove has arectangular cross-section.
 6. A flexible display device according toclaim 1, wherein the groove has a rounded cross-section.
 7. A flexibledisplay device comprising: (a) a flexible substrate having a first andsecond surfaces; (b) a plurality of display pixels arranged in a form ofrows and columns on the first surface of the substrate; (c) a pluralityof first parallel grooves in the first surface of the substrate, thefirst groove being formed in between adjacent two rows or columns of thedisplay pixels, thereby providing flexibility to the display device and,at the same time, minimizing the propagation of mechanical stress causedwhen the display device is bent or rolled; and (d) a plurality ofconnection lines for electrically interconnecting the plurality ofdisplay pixels.
 8. A flexible display device according to claim 7,further comprising a plurality of second parallel grooves, each of whichis formed in between adjacent two columns or rows of the display pixelsthereby enhancing the flexibility of the display device, the first andsecond grooves being substantially perpendicular to each other.
 9. Aflexible display device according to claim 7, wherein each first grooveis provided in between each adjacent rows or columns of the displaypixels.
 10. A flexible display device according to claim 7, wherein partof the connection lines is provided on the second surface of thesubstrate.
 11. A flexible display device according to claim 10, whereinthe connection lines comprise: (a) a plurality of row connection linesprovided on the second surface of the substrate, each row connectionline corresponding to each respective row of display pixels; (b) aplurality of column connection lines provided on the second surface ofthe substrate, each column connection line corresponding to eachrespective column of display pixels; and (c) a plurality of verticalconnection lines each connecting each display pixel on the first surfacewith a corresponding row or column connection line on the secondsurface, wherein an insulation layer is provided between the row andcolumn connection lines.
 12. A flexible display device according toclaim 11, wherein the vertical connection line includes a columnvertical connection line and a row vertical connection line, whichconnect a display pixel to a corresponding column and row connectionlines respectively.
 13. A flexible display device according to claim 11,wherein each display pixel is provided with a column vertical connectionline and a row vertical connection line, which connect the display pixelto a corresponding column and row connection line respectively.
 14. Amethod of manufacturing a flexible display device, the method comprisingthe steps of: (a) providing a flexible substrate having a first andsecond surface; (b) forming a plurality of first parallel grooves in thefirst surface of the substrate, each adjacent two parallel groovesdefining a pixel area therebetween; (c) providing a plurality of displaypixels on the pixel area such that the display pixels are arranged in apattern of rows and columns; and (d) providing a plurality of connectionline to electrically interconnect the display pixels.
 15. A methodaccording to claim 14, further comprising a step of forming a pluralityof second parallel grooves in the first surface of the substrate suchthat the second groove is substantially perpendicular to the firstgroove.
 16. A method according to claim 14, wherein, in the step offorming a plurality of first parallel grooves, the grooves are formed bymeans of a metal masking and patterning process and a reactive ionetching (RIE) process.
 17. A method according to claim 14, wherein, inthe step of forming a plurality of first parallel grooves, the groovesare formed by means of a laser micromachining process or a projectionlaser micromachining process.
 18. A method according to claim 14,wherein the step of providing a plurality of connection line comprisessteps of: (a) providing a first connection line to connect the firstsurface with the second surface of the substrate; and (b) providing asecond connection line on the second surface of the substrate such thatthe first connection line serves to electrically connects the displaypixel on the first surface to the second connection line on the secondsurface.
 19. A method according to claim 18, wherein the step ofproviding a first connection line comprises steps of: (a) forming athrough-hole passing through the first and second surfaces of thesubstrate; and (b) carrying out metallization in the through-hole.